Regional, mid-south US. From the Jerry Lee Lewis song "Drinkin' Wine Spo-Dee-O-Dee". Not quite an insult. The term is applied to one who is respected, yet inferior, or more often simply in a temporary state of inferiority, such as a friend who is being a stupid drunk.

as spoken to a friend who is hitting on fat girls and about to fall down some stairs: "whoa! careful there spo-dee!"

as a polite but firm and assertive warning to a transgressive stranger: "best keep off of my girl there spo-dee"